Mathematical calculation of lifespan of transfused RBCs in sickle cell disease patients

Background: Transfusion of donor red blood cells (RBCs) remains an important part of management of sickle cell disease (SCD). However, the survival characteristics of transfused donor RBCs in SCD patients have not been well studied. We sought to calculate survival kinetics of transfused RBCs in SCD patients since it is unclear whether transfused RBCs get destroyed at faster rate as innocent bystander or persist longer due to decreased destruction capacity such as functional splenectomy. Study design: and methods Forty-one SCD patients who had undergone at least 3 RBC exchange procedures were inlcuded. Interval between the procedures, both pre-procedure and post procedure hematocrits, HbA% and HbS% were collected. We developed a mathematical model to calculate RBC lifespan for donor RBCs. Results: Donor RBCs exhibited average lifespan of about 120 days (121.1 ± 13.9 days), which was similar to reported survival of RBCs in normal recipients. However, significant variation between patients were observed with lifespan ranging from 75.6-148.5 days. Intrapersonal variations were small in most cases. Conclusion: The calculated survival of donor RBCs in SCD recipient, based on certain laboratory values, appears to be similar to that of normal recipient. However, inter-personal variations were large, suggesting different RBC kinetics in a subset of patients, which calls for further research to better understand underlying pathophysiology. This knowledge of RBC survival would be very helpful in individualized management of patients on chronic RBCx.